Technological Field
The present technology relates to three-dimensional (3D) integrated circuits and, in particular, to providing interlayer conductors to multiple planes of circuits in the devices.
Description of Related Art
In the development of integrated circuits with high density, transistor structures are being created that have thin film channels and other structures with thicknesses on the nanometer scale. For example, 3D integrated circuits include multiple active layers in which thin film semiconductor layers are configured as active devices such as logic transistors, switching transistors and memory transistors. In some types of 3D memory integrated circuits the arrays comprise stacks of two-dimensional arrays of memory cells. Active layers in the stacks can include bit lines or word lines, for example, which must be connected to peripheral circuits like decoders, sense amplifiers and the like. In some arrangements, the connections are made using interlayer conductors that extend from each active layer to a routing layer, such as a patterned metal layer that overlies the stacks of two-dimensional arrays. The patterned metal layer can be used to route signals and bias voltages between the arrays and the appropriate peripheral circuits. Similar signal routing structures can be used on other types of 3D integrated circuits.
In the manufacturing of such devices, an important step involves making interlayer conductors that contact only one active layer, or only the intended active layers, and that can make successful contact with nanometer scale thin films.
It is desirable therefore to provide manufacturing techniques which improve the reliability and manufacturing margins in the formation of interlayer conductors that may contact the thin film active layers.